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Help - Pickup Phasing and hookup question

Discussion in 'Pickups & Electronics [BG]' started by Bassamatic, Sep 29, 2009.

  1. Bassamatic

    Bassamatic keepin' the beat since the 60's Supporting Member

    I picked up a great old Yamaha BB-400 with a reverse P setup. I decided to add a second reverse P to make a bass like Lee Sklar plays.

    I had it routed and added a nice fat Bart 8S in the new bridge position. Now that it is all wired up, I find some phase problems with the E and A strings when both Pups are on.

    Doing some checking, I find that the 2 halves of the Yamaha Pup are out of phase with each other, but the Pup is not humbucking like the Bart is. I have noticed this with other early Japanese P style Pups. The 2 halves of the Bart and my Fender and every other P pickup I could find ARE in phase with each other.

    SO - how do I solve the problem and make it all work? Is it as easy as reversing the wires between the 2 halves of the Yamaha Pup?

    I am curious as to why they are reversed from each other, but not humbucking.

    Thanks for your help.
  2. Yep, it is. The way P pups work is, the wiring is reverse-wound on one half, which essentially makes it electrically out of phase with the other half, to cancel noise.
    The magic that makes it still work? The magnets are also reversed on one half. This arrangement cancels noise, but puts the string vibrations back in phase. Clever.
  3. Bassamatic

    Bassamatic keepin' the beat since the 60's Supporting Member

    Ah - I get it - the magnetic polarity is reversed and so are the windings, so the noise is canceled and the output from the strings is IN phase. Clever!! Great to learn something significant each day.

    So - How do I fix this issue with the Yamaha Pup? It seems that they did not reverse the field as in the Fenders. Maybe it was a Patent issue. Sounds like the only solution is to change the Pup to a newer one. The problem is that the Yamah Pup mounting holes are about 1 screw diameter farther apart than the standard P Pup. Difficult to work with .
  4. Take a look at this. See the wire that's labeled 'black?' Swap it with the short wire that joins the halves, and use the joining wire as the output instead.
    You then may find that the PAIRS are out of phase when run together. In that case, just reverse the output wires (the ones that go to the pots)of one pair.
  5. I think you'll find that the magnetic fields ARE reversed a' la fender- that patent expired decades ago.
    To prove it, place the upward, string facing sides of the pup together. You will find that they stick together. Opposites attract.
  6. Bassamatic

    Bassamatic keepin' the beat since the 60's Supporting Member

    Thank you, dmusic148. That was my guess, but I thought I would check with the experts first. It is easy to check the phase of the output using a voltmeter and a metal object, so I will be sure that they are consistent.

    Both of the basses I have seen this in are from the 80's.

    Thanks for your help. I can't wait to play it.
  7. i have the same problems any time i get a P pickup with any other pickup... if i had only a single coil pickup and a HB then i would reverse the groud and hot on one of the pickups and the problem would be solved... with Ps you need to experiment to find the right wiering combination so that it works for every pickup individualy as well as when both are together...

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